Rope chains made from precious metal have for decades been made largely by hand. The basic construction element or component of such rope chains is a ring or link formed from a solid or hollow wire of precious metal, e.g. 14 karat gold. Such a ring 1 is shown in FIG. 1 and has an opening or gap (g) formed therein This gap g has a narrow dimension 2 at its inner diameter and a wider dimension at its outer diameter. The narrow dimension 2 of the gap g is slightly larger than the cross-section of the wire forming the ring 1, so that one ring can be inserted through the gap of another ring.
A multiplicity of such rings I are intertwined to form, in outward appearance, a double helix as shown in FIG. 2, which is the format of a standard rope chain. These tightly interfitting ring rope chains are generally hand made. However, machines have been developed to make rope chains, but these machine made chains generally have an inferior appearance than the hand made ones.
The wire forming the ring (FIG. 3) has a generally circular cross-section with slightly flattened sides 4 and rounded ends 5 which give the ring 1 a major dimension 6 and a minor dimension 7. The gap g of ring 1 is substantially larger than the minor dimension 7 and slightly larger at its narrowest dimension 2 than the major dimension 6, so that one ring can fit into another ring through the gap at any angle.
The reason for the slightly flattened sides 4 of the cross-section of the ring wire is a result of the process for making the round wire links and comes about as follows. The precious metal wire, generally having a circular cross-section, is wound around a mandrel to form a spiral coil. The coil is then cut so that each loop is cut slightly askew of its adjacent loop, resulting in accentric wire links having gaps accentrically aligned. In order to straighten these accentric links to be planar, the links are passed between pressure rollers or other pressure means to force the gap ends into the same plane. This pressure exerted on the planar surface of the rings causes a slight flattening of the cross-section of the ring wire. For all intents and purposes, this slight flattening is insignificant and results in a ring wire cross-section having major 6 and minor 7 dimensions a ratio of 1.1:1 to about 1.2:1. In the making of rope chains, such slightly flattened rings were treated as substantially being of round cross-section.
For the longest time these rope chains were made from split annular rings having approximately a 3:1 ratio of ring inner diameter to major wire dimension. Benhamou, U.S. Pat. No. 4,651,517, discovered that it is possible to substantially reduce the amount of precious metal required to make a rope chain of equivalent width and length by using a thinner wire annular ring and changing the ratio of ring inner diameter to major wire dimension to just over X times greater than the major wire dimension, where X is an odd number greater than three. In effect, by having the ratio of ring inner diameter to major wire dimension of approximately 5:1, 7;1 etc., one obtains according to this patent rope chains of similar diameter and length as the 3:1 ratio rope chain with significant reduction of weight.
A further improvement in weight saving in the manufacture of rope chains was claimed in my earlier patent, U.S. Pat. No. 4,996,835. In this patent, I disclose that substantial further weight saving can be obtained in the making of rope chains by using non-circular elongated shaped rings having a major axis defining longer outer and inner diameters and a minor axis defining shorter outer and inner diameters, and wherein the gap lies in a link section parallel to the major axis, and the shorter inner diameter being just over X times greater than the cross-section of the link wire, where X is a number equal to or greater than two, and the links are positioned in the chain so that the longer outer diameter defines the width of a chain.
To briefly summarize the development in improved rope chains, we can say that lighter rope chains, i.e. less weight of gold, having the same outer dimensions and appearance than the classical 3:1 ratio round link rope chains, can be obtained by either enlarging the inner ring diameter and introducing into the inner diameter more but thinner links (U.S. Pat. No. 4,651,517) or by changing the configuration of the chain link from a round configuration to an elongated configuration with the longer dimension providing the outer diameter of the chain. Both of the above described improvements have deviated from the classical rope chains made from round rings having apprxoimately a 3:1 ratio of inner ring diameter to wire cross-section diameter.
It is the object of the present invention to provide a precious metal rope chain with substantial weight saving.
Another object of the invention is to provide such a weight saving with a rope chain using classical round rings having a 3:1 ratio of inner ring diameter to major wire cross-section dimension.
It is a further object of the invention to provide improved weight saving in fine jewelry rope chains made with links having any shape whether round, elongated or polygonal.
Yet a further object of the invention is to provide fine jewelry rope chains having a silkier appearance than corresponding chains, whether these chains are made from round classical links with a 3:1 ratio or the Benhamou links with a ratio of 5:1 or 7:1 or the elongated links of my previously mentioned patent.
In accordance with this invention, there is provided a jewelry rope chain having tightly interfitting links made of wire of a given cross-section, each link having a small gap formed therein, so as to enable one of said links to pass through the gap of a second link, said links being intertwined to fit tightly one against the other and form in outward appearance a double helix, the improvement comprising each link having a wire cross-section including a major axis defining a longer dimension and a minor axis defining a shorter dimension, said longer dimension being in the plane of the link and the shorter dimension being perpendicular thereto, the ratio of said longer dimension to said shorter dimension being greater 1.3:1 but less than 3:1.
In a preferred embodiment, the gap of the link is narrower than the longer dimension of the wire cross-section.
The specific shape of the cross-section of the link wire is unimportant as long as the ratio of longer to shorter dimensions is maintained. Thus, the shape may be rectangular, rectangular with rounded edges, diamond shaped with rounded edges on the longer diameter, round with flattened sides, oval or elliptical, elongated hexagonal or octagonal etc.
Since the planar configuration of the links in accordance with this invention have the same configuration as corresponding conventional links, they can be used in the same manner as their corresponding conventional links in the preparation of rope chains. However, because the links in accordance with this invention are thinner, the gap in the links should be smaller than the large dimension of the wire cross-section and preferably only slightly larger than the shorter dimension of the wire cross-section. This gap size is important, since a larger gap will generally result in a loose chain with too much twist to it.
The discovery of this invention is remarkable and quite surprising, particularly since wire links having slightly flattened cross-sections have been known in the art for so many years. The significant advantage obtained by increasing the ratio of the major to minor dimensions of the wire cross-section to greater than 1.3:1 was totally unappreciated. This is evident from U.S. Pat. No. 4,651,517 which in order to achieve a reduction in weight for the rope chain, found it necessary to depart from the classical 3:1 ratio to a higher ratio of 5:1, 7:1 etc., while at the same time reducing the entire cross-section of the wire links. According to the present invention, a rope chain made with links having a wire cross-section as defined, even with links having a 3:1 ratio, provide significant weight saving over the rope chains made with conventional cross-section wire links, even over chains made according to U.S. Pat. No. 4,651,517 with links having a ratio of inner link dimension to wire cross-section of 5:1.